Unwanted plants, such as weeds, reduce the amount of resources available to crop plants and can have a negative effect on crop plant yield and quality. Unwanted plants in crop plant environments include broadleaves, grasses and sedges.
Herbicides are used to control weeds in crop environments. Herbicides are expensive, and their use may result in unintentional consequences such as groundwater contamination, environmental damage, herbicide-resistant weeds, and/or human and mammalian health concerns. It is therefore desirable to minimize the amount of herbicides applied to a crop-growing environment or any area in need of weed control.
Weeds may greatly reduce yields of crop plants. For example, a weed infestation reportedly was responsible for an 80% reduction in soybean yields. Bruce, J. A., and J. J. Kells, Horseweed (Conyza Canadensis) control in no-tillage soybeans (Glycine max) with preplant and preemergence herbicides, Weed Technol. 4:642-647 (1990). Therefore, controlling weeds is a major concern of crop growers.
Further, weeds are becoming resistant to the widely-used herbicide glyphosate. As early as 2000, glyphosate-resistant horseweed was reported in Delaware. Glyphosate-resistant horseweed has since been reported in numerous states. Accordingly, there is a need for new products that can provide effective kill rates of glyphosate-resistant weeds.
Weeds are also becoming resistant to herbicides that inhibit acetolactate synthase (ALS) and protoporphyrinogen oxidase (“PPOase”). Weeds have also been reported to be resistant to 2,4-D and dicamba. Accordingly, there is a need for new technology to control weeds that are resistant to commercially available herbicides.
In most fields throughout the Midwest and Mid-South, in-crop burndown applications are the only options for controlling weeds due to weather and timeliness of applications. Growers often find an active ingredient that is effective and then use it repeatedly. Eventually, the weeds become resistant to the active ingredient which leaves no alternatives for weed control other than mechanical removal. Mechanical removal of weeds requires extensive use of resources and is not an option for no-till or highly erodible land.
No-till farming has been increasing in popularity because it has many benefits, including decreased labor time and decreased soil erosion. However, one of the downsides of no-till farming is that weeds are harder to control in these areas because they are not subjected to tilling. Accordingly, there is an increasing need for alternative ways to handle weed infestation.
PPOase inhibitors are light activated herbicides. PPOase inhibitors work by inhibiting PPOase, which is a key enzyme in the synthesis of porphyrin containing compounds (e.g. chlorophyll and cytochrome). The inhibition of PPOase leads to both a lack of proper chlorophyll production and also an accumulation of protoporphyrin, which when exposed to light interacts with molecular O2 to produce single oxygen atoms that are highly toxic to cells.
Herbicides are often mixed with adjuvants to increase their effectiveness. Common adjuvants include crop oil concentrate, and “premium” adjuvant systems such as Dyne-a-Pak (available from Helena Chemical Company) which includes a proprietary blend of alkoxylated triglycerides, urea, ammonium nitrate, trisiloxane, methyl soyate, and the amine salt of alkyl ethoxylate phosphate. It is unpredictable which adjuvants out of the hundreds available would enhance the effectiveness of any herbicide against specific weeds. Further, even if an adjuvant provides increased efficacy against the weeds, it must also not increase phytotoxicity to the crop plant.
In summary, there is a need for a composition that reduces the amount of herbicides necessary to obtain sufficient weed control while minimizing the harm to crop plants. As more weeds become resistant to herbicides, alternative compositions with high weed control are desired. Further, as no-till farming continues to increase in popularity, there is a greater need for effective herbicides. A composition with effective weed control and lower dosage rate will lead to increased crop plant yields, and decreased environmental, human, and mammalian health concerns.